For the reproduction of pulses representing digital signals, preferably as recorded on magnetic tape, it is necessary to derive a timing signal for the purpose of signal regeneration. Such timing signal desirably continues even in the case of signal drop-outs. It is known to produce such timing signals by means of "flywheel" circuits. However, such circuits have the drawback that, in the absence of synchronizing pulses, the variable oscillator may oscillate at an arbitrary frequency which does not correspond to the desired frequency. Indeed, especially in the case of magnetic recordings, the desired frequency may vary from instant to instant depending on the speed of the tape.